You’ll get the following error:
[5:06] Download failed. Please download https://dl-ssl.google.com/android/repository/android_m2repository_r29.zip and put it to the C:UsersuserAppDataLocalXamarinXamarin.Android.Support.Design188.8.131.52 directory.
[5:06] Reason: The remote server returned an error: (407) Proxy Authentication Required.
I’ve come to rely on my trusted hacking friend Fiddler and turn on “Automatically Authenticate”.
Optionally configure your upstream proxy in Fiddler:
Restart Visual Studio so it picks up Fiddler as the proxy and you’re good to go. Just leave Fiddler running in the background and all will be well.